1. Field of the Invention
The present invention generally relates to a method for achieving uniform expansion of a dielectric plate and an electric connector made in accordance therewith.
2. The Prior Art
A computer central processing unit (CPU) is mounted to a main computer board by means of a connector. Conventionally, the CPU connector has contacts extending beyond top and bottom faces thereof for electrical engagement with pins of the CPU and conductive traces of the main board. The contacts are soldered to the main board by a through hole technique. Such a connector structure occupies a substantial amount of space on the main board and requires a sophisticated process to mount the connector thereto.
A ball grid array (BGA) connector effectively overcomes the problems discussed above. As shown in FIG. 8 of the attached drawings, a BGA connector 8 comprises a dielectric base plate 83 defining a number of contact receiving passages 80 therein between top and bottom faces thereof for receiving and retaining conductive contacts 81. Each contact 81 has a solder support section 82 extending beyond the bottom face of the base plate 83. A solder ball 9 is attached to the solder support section 82 by heating the solder support section 82 in advance. The solder balls 9 may be molten and fixed to a circuit board (not shown) by a heating process which provides an efficient and effective way for soldering the connector 8 to the circuit board.
Since the base plate 82 of the connector 8 and the circuit board are generally made of different material having different thermal expansion coefficients, heating the solder balls 9 to fix the contacts 81 to the circuit board will result in different amounts of thermal expansion of the circuit board and the base plate 83 leading to an undesired strain induced in the solder balls 9.
Furthermore, the base plate 83 is usually made by injection molding. During the molding process, a plasticized dielectric material is injected into a mold. Due to the complicated configuration of the base, a non-uniform distribution of the molecules of the dielectric material will result leading to different thermal expansion coefficients in different directions of the base plate 83 when the base plate 83 is heated during a BGA soldering process. Such non-uniform thermal properties magnify the above problem.
Thus, it is desired to provide a method for achieving substantially uniform thermal expansion of a dielectric plate in order to alleviate the problems discussed above.